1. Field of the Invention
The invention relates to measurement of high temperatures in chemical reactors. It is specifically directed to measurement of temperatures in catalytic reactors where endothermic reactions are carried out at high temperatures. In the petrochemical industry autothermal reformers are operating under these conditions.
2. Description of Related Art
In autothermal reformers or gasifiers the process gas entering the catalyst bed is typically 1000–1500° C., and the process gas contains hydrocarbons, hydrogen, carbon monoxide, water vapour and sometimes nitrogen. Under these severe conditions the temperature is most often not measured.
A temperature measurement arrangement is disclosed in U.S. Pat. No. 6,302,578 showing a thermowell installed in a thick reactor wall. This is done in such a way that there is a layer of hotface brick between the interior of the reactor and the tip of the thermowell with thermocouple, which thereby is protected against the high temperatures.
In PCT/US91/05432 another high temperature measurement is described. Here the thermocouple is protected by means of layers of ceramic insulation and a ceramic sheath.
However, these instruments are shielded from the reaction gasses and will not give an immediate indication of temperature changes of the gases. This is especially important for temperature of gasses entering a catalyst bed in autothermal reformers, as this temperature is extremely sensitive to changes in flow ratio between hydrocarbon feed and oxygen source.